SCIENTISTS believe they have discovered why psychological stress
can lead to physical pain.

A research team at Carnegie Mellon University in Pitts- burgh
found that chronic psychological stress is associated with the body
losing its ability to regulate the inflammatory response.

Published in the Proceedings of the National Academy of Sciences,
the research shows the effects of psychological stress on the body's
ability to regulate inflammation can lead to the development and
progression of disease.

Sheldon Cohen, professor of psychology at the university's
Dietrich College of Humanities and Social Sciences, said prolonged
stress alters the effectiveness of cortisol to regulate the
inflammatory response because it decreases tissue sensitivity to the
hormone.

Specifically, immune cells become insensitive to cortisol's
regulatory effect and in turn inflammation is thought to promote the
development and progression of many diseases.

Prof Cohen: "Inflammation is partly regulated by the hormone
cortisol and when cortisol is not allowed to serve this function,
inflammation can get out of control."

The professor, whose early work showed that people suffering from
psychological stress are more susceptible to developing colds, used
the common cold as the model for testing his theory. With the common
cold, symptoms are not caused by the virus. They are instead a side-
effect of the inflammatory response that is triggered as part of the
body's effort to fight infection.

The greater the body's inflammatory response to the virus, the
greater is the likelihood of experiencing cold symptoms.

Prof Cohen said: "The immune system's ability to regulate
inflammation provides an explanation of how stress can promote
disease."